PITTSBURGH — Thirty protesters were arrested Wednesday during a demonstration for a labor union and higher employee wages at the University of Pittsburgh Medical Center, organizers said.

UPMC officials didn’t comment on the events organized by the Service Employees International Union outside UPMC’s Pittsburgh headquarters.

The protest was peaceful but snarled downtown Pittsburgh traffic nearby, according to reports.

Union officials say UPMC has retaliated and fired employees who supported unionization.

Earlier, three union janitors, two union officials and a minister were cited for trespassing for refusing to leave UPMC’s Aiken Medical Building next to UPMC Shadyside Hospital.